Gardening in March: What to Do when the Temperature Drops Below Freezing

Updated: Mar 15



Some of you may have had a frost last night depending on your location, but tonight and Sunday are especially concerning with some predictions for our area being as low as 17 degrees! So what are we going to do at Painters with all of those beautiful plants outside that have been enjoying a mild March? And what should you do at home?


At Painters we will be leaving perennials outside that have been thoroughly 'hardened off' (acclimated to the cold); our creeping phlox and heuchera for example have been grown outside all winter. Ideally we'd protect every plant from potential frost burn, but we only have so much covered space (and time!). We are however going to move our budding/blooming berry bushes, fruit trees and spring blooming trees into our cold frame for a little extra protection. We will also bring most of our bedding annuals and cold season veggies inside, but put frost cloth over our pansies, violas and hellebores with blooms as they've been outside a long time and are pretty cold tolerant plants.


So what does this mean for you at home? Shrubs, evergreen vegetation, and plants that are well established and mostly dormant are all fine, but you may want to protect things with tender new growth or buds/blooms. Can you cover that giant Jane Magnolia tree that is your pride and joy or the hundreds of daffodils lining your driveway - probably not! Do what is within your ability, and just emotionally prepare yourself for the likelihood that this is the last of your magnolia, cherry, or daffodil blooms for the season. Below are items we do recommend covering, or if in pots, moving to a covered porch or garage:

YOUNG FRUITING TREES AND SHRUBS

For those of you with a lot of fruiting shrubs and trees, especially if you're just starting your edible landscape and they're young/small enough to easily cover, there are some great frost blankets worth investing in for each early spring and potential late frosts. This landscaping site has some great information on trees in general, and a helpful blog about covering fruit trees! If you don't have time/the funds to acquire specialized frost cloths that allow for ideal moisture exchange, try layering sheets or regular frost cloth to give extra protection to fruits and other items you're especially worried about, and just remember to open up to cloth during the day to allow some air exchange if keeping covered for multiple nights!


BLOOMING PLANTS

Anything that you’ve bought from us since we opened may get some frost damage even if they are cold-hardy plants like violas and pansies. Snapdragons, dianthus, columbine and lupines are some of the ones we are protecting and we recommend that you do so too if you can. The cold shouldn't kill these plants, (though how long you've had them outside and if they are in the ground vs in a pot may be a determining factor), so if you can't get them all covered don't panic. You may want to make some big bouquets with the blooms you are likely to lose - daffodils are quite cheery and you may not have any more blooming after this cold. If you purchased any of our beautiful lupines and aren't able to cover them all (even then they may get damaged depending on temps), these also make lovely cut flowers. NOTE: A lot of spring bloomers are toxic to pets and humans if ingested - lupines and daffodils are both quite toxic so bouquets should be kept out of reach of pets (especially cats) and toddlers, and also note that daffodils need a vase to themselves as their sap is actually toxic to other plants!



VEGGIES AND HERBS

While some cold crop veggies can be pretty tough, we still recommend covering them for temperatures this low. If you do end up with frost burn on your lettuce or kale, just trim off super damaged leaves - more will follow! Definitely try to protect freshly planted veggies or new sprouts emerging from direct sown crops such as peas. While a lot of herbs are hardy, many are very sensitive to the cold - if you have dill, basil, or other annual herbs it would be best to bring them inside. For perennial herbs such as rosemary, lavender or sage, they are likely OK outdoors but would be happiest with some protection/cover - especially if you bought them from inside our greenhouse or inside another protected/warm greenhouse (meaning they haven't been hardened off yet).



POTTERY

If a pot is considered frost resistant it should be OK (if purchased at Painters, anything outdoors is frost resistant). If you don't know if yours is (any pottery purchased from Painters indoor area is not), then it's best to tuck it under a covered porch or inside. Note that when pots do crack due to cold it's typically because of water expansion - good drainage is key in preventing this, so if you have a pot with really saturated soil and very little drainage it will be at more risk of damage.


OK, so what do I cover things with??

Maybe you only have so much frost cloth, or maybe you have none. While frost cloth or a tightly woven blanket may give you the best protection, sheets can help as can old pots! Still have a bunch of pots left from planting? Place them over top smaller plants (ideally not touching the plant) with a rock on top - it helps! Most critically, when covering plants it really makes a difference when you prop the cover off of the foliage/blooms - if the cover is touching the plant, you will likely have some damage in those spots. Bamboo or garden stakes and lawn furniture can be helpful when propping cloth off plants!


Good luck!


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